1. Technical Field
The invention concerns a semiconductor component comprising a first integrated circuit in a substrate which is adapted to produce electrical signals with a high-frequency signal component, wherein the substrate is such that the high-frequency signal component can propagate on a substrate surface and/or in the substrate interior, a second integrated circuit in the same substrate, which is such that the function thereof can be compromised by high-frequency electrical signals, and a countersignal circuit in the same substrate which is adapted to deliver an electrical countersignal which at least at a selected location of the substrate surface and/or of the substrate interior attenuates or eliminates the high-frequency electrical signal component emanating from the first integrated circuit.
2. Discussion of Related Art
Progressive integration in microelectronics, besides a reduction in the component dimensions, also permits novel integration of various functions in a semiconductor device. Due to the development, which has been meteoric especially in recent times, in technologies in microelectronics such as for example the BiCMOS process and in particular the SiGe:C technology (use of a carbon-bearing silicon-germanium alloy in production of the semiconductor device), it is possible for example to combine at the same time highly complex digital circuits and less complex but highly sensitive analog circuits on a substrate.
Hitherto the analog circuits for high-frequency signal processing in receivers and transmitters, for example in the medium and upper GHz range, were implemented using GaAs technology whereas the corresponding digital signal processors were embodied in the less expensive silicon technology.
The development of higher frequency ranges using silicon technology, in particular by virtue of SiGe:C technology, has now made it possible to integrate digital and analog circuits in a single semiconductor device, in particular on a chip based on SiGe:C technology. Integration in a single chip results in a reduction in the surface area required and thus results in shorter conduction paths, which in turn permits an increase in the operating speed of the chip and reduces current consumption.
The signal/noise ratio can be markedly increased. A further advantage of integration is that the costly GaAs technology can be avoided.
Therefore the above-indicated integration, by virtue of the short paths and the reduced current consumption, considerably increases the functionality of the integrated semiconductor device.
At the present time however, because of the problems which have not yet been resolved in the state of the art, such as in particular mutual crosstalk of the signals of the two circuit portions, the advantages of such integration cannot yet be used in a practical context. The term crosstalk is used here to denote capacitive or inductive coupling of in particular high-frequency signal components of a first circuit, as an interference signal, into a second circuit. In the second circuit the interference signal is superimposed on the actual signal, that is to say the signal which is generated or which is to be processed in the second circuit.
In that respect, in most cases the substrate in which the integrated circuits are provided is of such a nature that the high-frequency signal component can propagate on a substrate surface or in the substrate interior or both on a substrate surface and also in the substrate interior. Those propagation alternatives are also combined together in the context of this application by the abbreviating expression ‘on a substrate surface and/or in the substrate interior’.
SOI-substrates which can reduce crosstalk by virtue of the embedded insulator layer require an increased level of process complication and expenditure in manufacture and cannot completely suppress capacitive coupling of high-frequency interference fields. Relatively good passive shielding is achieved with an earthed ground shielding for example in the form of a buried channel.
In digital circuits, high-frequency alternating fields occur for example due to clock generation in the digital processor. The clock frequency itself is for example frequently about 40 MHz. That frequency can already be found to cause disturbance in adjacent sensitive analog circuits and in the context of this application is referred to as high-frequency. In addition alternating fields produced by digital circuits, because of the steep edges of the clock signal, have a frequency spectrum with a particularly pronounced signal component in the high-frequency spectral range above the clock frequency itself. High-frequency interference fields can however also be caused by signals in an intermediate frequency range. As is known, intermediate frequency signals are produced in the production of a radio signal to be emitted in a transmitter circuit. The frequency thereof can be for example 800 MHz while the actual transmission frequency is in the gigahertz range.
By way of example voltage-control oscillators and signal generators, as in the above-mentioned example of clock signal generation, are considered as a source for interference signals which are produced in digital circuits.
High-frequency alternating fields produced by digital circuits are received for example by a highly sensitive amplifier (low noise amplifier—LNA) of an analog circuit portion and amplified in such a way as to result in unwanted superimposition phenomena with the actual signal of the analog circuit portion. Such superimposition phenomena worsen the signal quality or completely prevent functioning of the analog circuit. Crosstalk has an effect in particular when there are small spacings between two circuits integrated in a substrate and is therefore in conflict with a reduction in the size of the structures in a chip.
Known approaches for reducing crosstalk involve separating the circuits which influence each other in terms of interference (for example analog and digital circuits), that is to say providing them in two different chips, or keeping the spacings between two circuits as large as possible. A further approach involves suppressing the interference signal by insulator layers between the circuits (see SOI). Semiconductor devices in which such approaches are used are described for example in EP 0 817 268.
DE 102 15 328 A1 proposes providing a countersignal circuit in a semiconductor component having a first and a second integrated circuit. The object of the countersignal circuit described therein is to produce a countersignal which leads to suppression of an interference signal. The countersignal circuit of DE 102 15 328 A1 is however not described in terms of its structural configuration.